Mucosal-associated Invariant Cells are Deficient in Systemic Sclerosis.

Systemic sclerosis (SSc) is an autoimmune disease, characterized by fibrosis of the skin and other organs, vascular impairment and deficient immune responses. Mucosal-associated invariant T cells (MAIT) have been involved in various inflammatory and autoimmune diseases. The aims of this study were to determine the frequencies of MAIT cells in the blood of patients with systemic sclerosis (SSc) and to compare their distribution in different types of SSc. Blood samples from patients with SSc and healthy controls were examined by flow cytometer to analyse the frequencies of MAIT and γδ T cells. We demonstrate that in SSc the frequencies and absolute numbers of MAIT and γδ T cells are significantly reduced in comparison with healthy controls. MAIT and γδ T cells did not correlate with C-reactive protein, BNP, pulmonary involvement or median skin fibrosis scale, steroid amount or disease duration. In addition, MAIT and γδ T cells decrease did not stratify with gender, interstitial lung disease or active digital ulcers. Functional studies are necessary to determine the signification of MAIT cells decrease in systemic sclerosis.

[Unexplained recurrent early miscarriages: Role of immunomodulation?] / Fausses couches précoces récurrentes inexpliquées : quelle est la place de l'immunomodulation ?

About 1-3% of women experience early recurrent miscarriages, defined by ≥3 fetal loss before 14 weeks of gestation. About half of these recurrent early miscarriages could be related to a genetic cause. Pre-implantation genetic diagnosis is used in several European countries, but it is still prohibited in France except for couples at risk for transmission of severe genetic diseases. The immune dysregulation, and in particular allo-immune excessive response, could be responsible for fetal loss in remaining cases, although currently we lack biomarker to confirm the immune-mediated fetal loss. Several immunosuppressive and immunomodulatory treatments have been the subject of small studies in patients with early recurrent miscarriages. The available data do not allow to define the treatment recommendations in this topic, and further studies are necessary.

Translational opportunities for targeting the Th17 axis in acute graft-vs.-host disease.

Allogeneic stem cell transplantation (allo-SCT) is a curative therapy for different life-threatening malignant and non-malignant hematologic disorders. Acute graft-vs.-host disease (aGVHD) and particularly gastrointestinal aGVHD remains a major source of morbidity and mortality following allo-SCT, which limits the use of this treatment in a broader spectrum of patients. Better understanding of aGVHD pathophysiology is indispensable to identify new therapeutic targets for aGVHD prevention and therapy. Growing amount of data suggest a role for T helper (Th)17 cells in aGVHD pathophysiology. In this review, we will discuss the current knowledge in this area in animal models and in humans. We will then describe new potential treatments for aGVHD along the Th17 axis.

Donor interleukin-22 and host type I interferon signaling pathway participate in intestinal graft-versus-host disease via STAT1 activation and CXCL10.

Acute graft-versus-host disease (aGVHD) remains a major complication following allogeneic hematopoietic cell transplantation, limiting the success of this therapy. We previously reported that interleukin-22 (IL-22) participates to aGVHD development, but the underlying mechanisms of its contribution remain poorly understood. In this study, we analyzed the mechanism of the pathological function of IL-22 in intestinal aGVHD. Ex-vivo colon culture experiments indicated that IL-22 was able to induce Th1-like inflammation via signal transducer and activator of transcription factor-1 (STAT1) and CXCL10 induction in the presence of type I interferon (IFN). To evaluate a potential synergy between IL-22 and type I IFN in aGVHD, we transplanted recipient mice, either wild-type (WT) or type I IFN receptor deficient (IFNAR(-/-)), with bone marrow cells and WT or IL-22 deficient (IL-22(-/-)) T cells. We observed a decreased GVHD severity in IFNAR(-/-) recipient of IL-22(-/-) T cells, which was associated with a lower level of STAT1 activation and reduced CXCL10 expression in the large intestine. Finally, immunohistochemistry staining of STAT1 performed on gastrointestinal biopsies of 20 transplanted patients showed exacerbated STAT1 activation in gastrointestinal tissues of patients with aGVHD as compared with those without aGVHD. Thus, interfering with both IL-22 and type I IFN signaling may provide a novel approach to limit aGVHD.

ATG-induced accelerated immune senescence: clinical implications in renal transplant recipients.

Persistent ATG-induced CD4(+) T cell lymphopenia is associated with serious clinical complications. We tested the hypothesis that ATG induces accelerated immune senescence in renal transplant recipients (RTR). Immune senescence biomarkers were analyzed at transplant and one-year later in 97 incident RTR -62 patients receiving ATG and 35 receiving anti-CD25 mAb (α-CD25). This consisted in: (i) thymic output; (ii) bone marrow renewal of CD34(+) hematopoietic progenitor cells (CD34(+) HPC) and lymphoid (l-HPC) and myeloid (m-HPC) progenitor ratio; (iii) T cell phenotype; and (iv) measurement of T cell relative telomere length (RTL) and telomerase activity (RTA). Clinical correlates were analyzed with a 3 year follow-up. Thymic output significantly decreased one-year posttransplant in ATG-treated patients. ATG was associated with a significant decrease in l-HPC/m-HPC ratio. Late stage differentiated CD57(+) /CD28(-) T cells increased in ATG-treated patients. One-year posttransplant T cell RTL and RTA were consequently lower in ATG-treated patients. ATG is associated with accelerated immune senescence. Increased frequency of late differentiated CD4(+) T cell frequency at transplantation tended to be predictive of a higher risk of subsequent opportunistic infections and of acute rejection only in ATG-treated patients but this needs confirmation. Considering pretransplant immune profile may help to select those patients who may benefit from ATG to prevent severe infections and acute rejection.

Increased Th17/Treg ratio in chronic liver GVHD.

The contribution of Th17 cells to chronic GVHD (cGVHD) has been demonstrated in cGVHD mouse models. However, their contribution to human liver cGVHD remains unclear. We evaluated Th17 cells in biopsies from a cohort of 17 patients with liver cGVHD. We observed a significant increase in Th17 cells in the liver of patients with cGVHD, as demonstrated by an increase in CCR6+, CD161+ and RORγt+ T cells (P=0.03, P=0.0001 and P=0.03, respectively). We also assessed the presence of Th1 and regulatory (Treg) T cells: the numbers of Th1 and Treg cells were very low, with no difference between the two groups (P=0.88 and P=0.12, respectively). Furthermore, Th17/Th1 and Th17/Treg ratios were significantly increased in the liver of patients with liver cGVHD (P=0.005 and P=0.002, respectively). This study provides evidence for an infiltration by Th17 cells in the liver of patients with cGVHD and an increased Th17/Treg ratio, suggesting a defect in the regulatory mechanism driven by Treg cells or an inappropriate activation of effectors cells, especially Th17 cells, or both mechanisms, in human liver cGVHD.

IL-22 deficiency in donor T cells attenuates murine acute graft-versus-host disease mortality while sparing the graft-versus-leukemia effect.

Acute graft-versus-host disease (aGVHD) remains a major complication following allogeneic hematopoietic cell transplantation (allo-HCT), limiting the success of this therapy. Many proinflammatory cytokines secreted following the conditioning regimen have been linked to aGVHD initiation. Interleukin-22 (IL-22) is a cytokine related to IL-10 for its structure and is secreted by T helper type 17 (TH17) cells and innate immune cells. Given the paradoxical role of IL-22 in inflammation with both protective or proinflammatory functions, we investigated whether IL-22 could have a role in aGVHD pathophysiology in a mouse allo-HCT model. In this study, we show that IL-22 deficiency in donor T cells can decrease the severity of aGVHD, while limiting systemic and local inflammation in aGVHD target organs. In addition, we found that Foxp3+ regulatory T cells (Treg cells) were increased in recipient mice that received IL-22-deficient T cells, suggesting that Treg were involved in the reduced severity of GVHD. Finally, we found that the graft-versus-leukemia (GVL) effect mediated by donor T cells was preserved in the absence of IL-22. Overall, these data suggest that targeting of IL-22 may represent a valid approach towards decreasing aGVHD severity after allo-HCT while preserving the GVL effect.

Plasmacytoid dendritic cells and Th17 immune response contribution in gastrointestinal acute graft-versus-host disease.

The contribution of Th17 cells in acute graft-versus-host disease (aGVHD) has been demonstrated in aGVHD mouse models. However, their contribution in human gastrointestinal aGVHD remains unclear. We evaluated Th17 cells in a cohort of 23 patients at diagnosis of aGVHD. In this study, we have shown that the absolute number of Th17 cells using the CCR6 and CD161 markers were significantly higher in the intestinal mucosa of patients with aGVHD compared with intestinal mucosa of patients without aGVHD. Moreover, in keeping with the increase of CCR6+ and CD161+ T cells, RORγt the key transcription factor that orchestrates the differentiation of Th17 cells, was significantly increased in the intestinal mucosa of patients with aGVHD compared with intestinal mucosa of patients without aGVHD (P=0.01). Since plasmacytoid dendritic cells (PDCs) have been reported to drive the differentiation of the Th17 subset, we quantified PDCs in these patients. PDC CD123+ cells were increased in the intestinal mucosa of patients with aGVHD. Furthermore, the number of CD123+ PDCs paralleled the histological grade of aGVHD, providing evidence for a role of Th17-mediated responses and a potential new pathophysiological link between PDCs and Th17 in human aGVHD.

Escalated lymphodepletion followed by donor lymphocyte infusion can induce a graft-versus-host response without overwhelming toxicity.

Treatment of relapse of hematological malignancies following allogeneic hematopoietic SCT (allo-HSCT) remains very challenging and relies usually on the readministration of chemotherapy combined with donor lymphocyte infusion (DLI). To enhance DLI effectiveness, lymphodepletion (LD) with fludarabine (Flu) and/or CY before the injection of lymphocytes is an attractive modality to modify the immune environment, leading possibly to suppression of regulatory T cells (T(reg)) and exposing the patient to cytokine activation. However, LD before DLI may lead to induction of deleterious GVHD. To avoid inducing overwhelming toxicity, we proceeded by escalating doses of both LD and DLI. Eighteen patients with various non-CML hematological malignancies who relapsed following allo-HSCT were treated with chemotherapy and LD-DLI or LD-DLI upfront. T-cell subpopulation and DC levels as well as cytokine plasma levels (IL-7, IL-15) were measured before and following LD-DLI. Cumulative incidence of acute grade II-IV GVHD was 29.4% similar to that reported in patients receiving DLI without LD. In addition, Flu alone with low dose of DLI was not associated with severe GHVD. CY/Flu at the respective doses of 600 mg/m(2) on day 1 and Flu 25 mg/m(2)/day on days 1-3 did not result in a marked decrease of T(reg) cells, nor in endogenous IL-7 and IL-15 production. However, a peripheral expansion of DCs was observed. These findings suggest that the escalated dose procedure appears safe and prevent overwhelming toxicity. A dose-limiting toxicity has not yet been reached.

[Towards the use of intravenous apoptotic leukocyte infusion as a cell-based therapy approach?]. / Vers l'utilisation thérapeutique de l'administration intraveineuse de leucocytes apoptotiques du donneur en thérapie cellulaire ?

In the past few years, significant advances have been performed in the field of cell-based therapies. This concerns mainly regenerative medicine with the use of stem cells, as well as the modulation of immune responses. In order to modulate allogeneic immune responses after transplantation, we have developed a cell therapy approach based on the immunomodulatory properties of intravenous donor apoptotic cell infusion. In allogeneic hematopoietic cell transplantation settings, we reported that intravenous apoptotic leukocyte infusion, simultaneously to allogeneic bone marrow grafts, favors hematopoietic engraftment, prevents alloimmunization and delays graft-versus-host disease. Here, we review the different factors and cells implicated in the immunomodulatory properties of apoptotic cells. Then, we discuss the potential significance of such observations in transfusion practice.

Impact of plasmacytoid dendritic cells on outcome after reduced-intensity conditioning allogeneic stem cell transplantation.

The reconstitution of the plasmacytoid dendritic cells (PDCs) compartment might influence outcome after allogeneic stem cell transplantation (allo-SCT). Thus, we investigated the impact of blood PDCs measured at the third month after reduced-intensity conditioning (RIC) in 54 patients who received an HLA-identical sibling allo-SCT. The absence of grade II-IV acute graft-versus-host-disease (GVHD) was associated with an improved PDC count at 3 months after RIC-allo-SCT (P=0.003; OR=6.4; 95% CI, 1.9-22). The CD34+ stem cell dose and other lymphoid subsets infused with the allograft did not affect PDC recovery. Although PDC count could not predict death from progression or relapse, patients with a "high" PDC recovery profile had an improved overall survival (OS; P=0.03), in contrast to patients with a "low" PDC recovery profile who had an increased incidence of nonrelapse mortality (GVHD, infections) (P=0.03). The overall incidence of late infections (viral, fungal and bacterial) was significantly higher in the "low" PDC recovery group as compared to the "high" PDC recovery group (59 vs 19%; P=0.002). In a multivariate analysis, only a "high" PDC count was significantly predictive of a decreased risk of death (P=0.04; RR=0.34; 95% CI, 0.12-0.96). Monitoring of PDCs at 3 months after RIC-allo-SCT may be a useful indicator predictor of long-term outcome.

Cytomegalovirus-specific immune recovery following allogeneic HLA-identical sibling transplantation with reduced-intensity preparative regimen.

Cytomegalovirus (CMV) represents a major cause of morbidity after allogeneic stem cell transplantation (allo-SCT). Using interferon-gamma-enzyme-linked immunospot (ELISPOT) assay and HLA-peptide tetramers, we analysed 54 patients who received a reduced-intensity conditioning regimen, including fludarabine, busulphan and antithymocyte globulin (ATG), with the aim of defining essential elements of protective immunity to CMV. The cumulative incidence of CMV positive antigenaemia was 37% occurring at a median of 43 days (range, 7-104) after allo-SCT. In univariate analysis, conditioning regimen (ATG dose) and graft characteristics (graft source and CD3+ T-cell dose) significantly influenced CMV-specific immune recovery. A significant correlation (P=0.000002) was found between CMV-specific T cells detected by IFN-gamma ELISPOT assay and pp65-specific CD8+ T-cell frequency quantified by tetramers. CMV-specific CD8+ T cells presented a phenotype of effector cells (perforin and 2B4 positive). In multivariate analysis, bone marrow (BM) as a graft source was the only variable associated with an increased risk of CMV positive antigenaemia (P=0.0001) in line with the ELISPOT assay showing a higher frequency of functional CMV-specific effectors within peripheral blood stem cell grafts as compared to BM. Thus, early monitoring of CMV-specific immune recovery using sensitive new tools might prove useful for patient management after allo-SCT.

Abundant expression of fibronectin is a major feature of leukemic dendritic cells differentiated from patients with acute myeloid leukemia.

Dendritic cells (DCs) are the most potent antigen-presenting cells responsible for the initiation of primary immune responses, playing a key role in eliciting effective antitumor immune responses. We reported previously that leukemic blasts from selected patients with acute myeloid leukemia (AML) were able to differentiate in vitro into cells with DC features. In order to identify genes differentially expressed in leukemia-derived DCs (AML-DCs), a polymerase chain reaction (PCR)-based subtraction approach was applied using cDNA from AML-DCs and monocyte-derived DCs from healthy donors as competitors. In the 548 sequences analyzed, 80% corresponded to fibronectin (FN) gene fragments. Overexpression of FN in AML-DCs was demonstrated both by semiquantitative PCR analysis and by immunostaining. In addition, we could show that FN was secreted by AML-DCs. Indeed, FN overexpression was already detectable in AML blasts of M4 and M5 subtype, and was significantly induced during DC differentiation after culture. Although the molecular events leading to overexpression of FN and the in vivo relevance of this phenomenon remain to be resolved, leukemic DCs appear to have specific patterns of differentiation, warranting stringent biological and cellular monitoring for the development and testing of leukemic DC-based immunotherapeutic strategies.

Dendritic cells: interfaces with immunobiology and medicine. A report from the Keystone Symposia Meeting held in Keystone, 3-8 March 2003.

Dendritic cells (DCs) are the most potent antigen-presenting cells in vitro and in vivo. They play a key role in the initiation of the immune response and are considered promising targets for immunotherapy. The recent DC Keystone Symposia, organized by Ralph M Steinman, Anne O'Garra and Jacques Banchereau, was held on 3-8 March 2003 in Keystone (CO, USA). This multidisciplinary meeting developed various areas related to the DC biology including: (i) DC and the control of immunity vs tolerance; (ii) DC maturation and manipulation for immunotherapy in vivo; and (iii) antigen capture by DC in situ and interactions with microbial pathogens. The aim of this report is to present some of the highlights developed during the meeting and debated among the DC community.

Leukemic dendritic cells: potential for therapy and insights towards immune escape by leukemic blasts.

Dendritic cells (DCs) are a system of potent antigen-presenting cells (APCs) specialized to initiate primary immune responses. DCs are considered important elements in the induction of specific antitumor cytotoxic effectors. At present, because of potential therapeutic implications, the critical role of DCs in cancer patients is under intensive investigation. Interactions between DCs and acute myeloid leukemia cells represent an attractive model for the study of DC physiology. Moreover, DCs can be a valuable therapeutic tool for the adjuvant treatment of leukemic patients. However, DC subsets in vivo may also be affected by leukemogenesis and may contribute to the escape of leukemia from immune control. The aim of this review is to shed further light on this paradoxical picture where the line between immune tolerance and immune defense is narrow.

Identification of precursors of leukemic dendritic cells differentiated from patients with acute myeloid leukemia.

Dendritic cells (DC) can facilitate immune responses that might help in the induction of effective antitumor T cell responses. We reported previously that leukemic blasts from selected patients with acute myeloid leukemia (AML) were able to differentiate in vitro into cells with mature DC features. However, despite the use of a wide variety of cytokine combinations, leukemic DC could not be obtained from all AML patients. In this study, we investigated in a wide range of AML patients (n = 30), the nature and functional characteristics of the blast compartment that can be induced to acquire DC features in vitro. Our results demonstrate that leukemic DC generated in the presence of GM-CSF, IL-4 and matured with CD40L, are composed of two major subsets: DC derived from CD14(+) leukemic cells and leukemic DC derived from in vivo expanded circulating blood myeloid DC (MDC). Leukemic DC of both subsets exhibited DC morphology, had a phenotype of mature DC, and could induce a potent proliferative response of naive CD4(+) T cells. Moreover, both subsets produced large amounts of IL-12p70 and leukemic CD14(+)-derived DC could induce a potent Th1 response. These results can be considered as a prerequisite before the design of vaccine immunotherapy protocols for the adjuvant treatment of AML patients.

Features of large granular lymphocytes (LGL) expansion following allogeneic stem cell transplantation: a long-term analysis.

Large granular lymphocyte (LGL) proliferation typically follows a chronic course during which major features are cytopenia and immune abnormalities. Elevated numbers of LGL were reported in a few cases following allogeneic stem cell transplantation (allo-SCT). In this report, we present a retrospective analysis of LGL cases that occurred following allo-SCT in a cohort of 201 consecutive patients transplanted over a period of 7 years. Six cases were identified and LGL expansion occurred more frequently following a reduced fludarabine and anti-T lymphocyte globulin-based preparative regimen (4 cases/49), than after a conventional myeloablative regimen (2 cases/152). Expansion of LGL was seen between 3 and 15 months following allo-SCT. Hematopoiesis, with mild to severe cytopenia, was a favored target for LGL. Autoimmune manifestations including polyarthritis and hypergammaglobulinemia were also observed. LGL proliferation was observed in the context of chronic antigenic stimulation associated with recurrent viral infections especially CMV. Moreover, five out of these six high risk patients achieved a long-term complete remission concomitant or following LGL expansion. These data suggest that LGL might be a subset of effector lymphocytes which may participate to the graft-versus-tumor effect.

Recovery of lymphocyte and dendritic cell subsets following reduced intensity allogeneic bone marrow transplantation.

Approaches using reduced conditioning regimens have been developed to obtain minimal procedure-related toxicity. Such novel therapeutic options are being explored with good preliminary results concerning feasibility and engraftment. However, many aspects remain under-evaluated and few data are available about immune and dendritic cell (DC) reconstitution after these highly immunosuppressive regimens. We present here our data in 20 patients receiving allogeneic bone marrow transplantation (allo-BMT) using a reduced preparative regimen. We evaluated in the first 3 months following allo-BMT, several immunological parameters including DC subsets, and compared these to historical results obtained in a group of myeloablative allo-BMT patients. We found an early recovery of leukocytes, CD8+ and NK lymphocytes. We also found a trend towards an improved B cell recovery. These results are somewhat in contrast to the altered immune recovery observed in the myeloablative setting. In addition, we found a significant early circulating DC recovery. Circulating blood DCs were also found to be of full donor origin as assessed by FISH in sex-mismatched pairs. Nevertheless, naive CD4 + CD45RA + T cells were found to be profoundly reduced following such regimens.Collectively, these data further enhance the overall benefits of reduced intensity regimens and the need for a stringent biological monitoring for assessment of the potential advantages of reduced intensity allo-BMT in comparison with conventional allo-BMT.

Circulating blood dendritic cells from myeloid leukemia patients display quantitative and cytogenetic abnormalities as well as functional impairment.

Dendritic cells (DCs) are responsible for the initiation of immune responses. Two distinct subsets of blood DCs have been characterized thus far. Myeloid DCs (MDCs) and plasmacytoid monocytes (PDCs) were shown to be able to promote polarization of naive T cells. This study shows a dramatic quantitative imbalance in both circulating blood DC subsets in 37 patients with acute myeloid leukemias. Eleven patients (30%) displayed a normal quantitative profile (MDC mean, 0.37% +/- 0.21%; range, 0.01% to 0.78%; PDC mean, 0.21% +/- 0.24%; range, 0.04% to 0.62%), whereas 22 (59%) showed a tremendous expansion of MDCs (9 patients: mean, 16.76% +/- 14.03%; range, 1.36% to 41%), PDCs (4 patients: mean, 7.28% +/- 6.84%; range, 1% to 14%), or both subsets (9 patients: MDC mean, 10.86% +/- 12.36%; range, 1.02% to 37.1%; PDC mean, 4.25% +/- 3.78%; range, 1.14% to 13.04%). Finally, in 4 patients (11%), no DC subsets were detectable. Both MDC and PDC subsets exhibited the original leukemic chromosomal abnormality. Ex vivo, leukemic PDCs, but not leukemic MDCs, had impaired capacity for maturation and decreased allostimulatory activity. Also, leukemic PDCs were altered in their ability to secrete interferon-alpha. These data provide evidence that DC subsets in vivo may be affected by leukemogenesis and may contribute to leukemia escape from immune control.